DTC C1A05: Stop Light Switch Circuit [09/2014 - 11/2017]: Procedure

1. Disconnect the A52 stop light switch assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Stop Light Switch Assembly)

2. Measure the voltage and resistance according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A52-1 (B) - A52-3 (GND)	Always	11 to 14 V
   A52-5 (B) - A52-3 (GND)	Engine switch on (IG)	11 to 14 V

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A52-3 (GND) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BATTERY AND BODY GROUND) 

Result: 

OK 

See step  2

1. Disconnect the Q1 driving support ECU assembly connector.
2. Disconnect the A52 stop light switch assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Q1-27 (STP-) - A52-2 (L)	Always	Below 1 Ω
   Q1-28 (ST1-) - A52-4 (L)	Always	Below 1 Ω
   Q1-27 (STP-) or A52-2 (L) - Body ground	Always	10 kΩ or higher
   Q1-28 (ST1-) or A52-4 (L) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Replace the stop light switch assembly.

   Refer to REMOVAL [09/2014 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  4

1. Clear the DTCs.

   Refer to DTC CHECK / CLEAR [09/2014 - 11/2017]

   Powertrain > Radar Cruise > Clear DTCs 

2. Make sure that the DTC detection conditions are met.

   HINT: 

   If the detection conditions are not met, the system cannot detect the malfunction.

3. Check for DTCs.

   Refer to DTC CHECK / CLEAR [09/2014 - 11/2017]

   Powertrain > Radar Cruise > Trouble Codes 

   NOTE:

   When replacing the driving support ECU assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle. As a result, a DTC may be stored.

   Result

   Result	Proceed to
   DTC C1A05 is not output	A
   DTC C1A05 is output	B

Result: 

A 

END (STOP LIGHT SWITCH ASSEMBLY WAS DEFECTIVE) 

Result: 

B 

REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  REMOVAL [09/2014 - 01/2023]